1. Organisms and the abiotic environment

2. Organisms and the abiotic environment
The Red River Pupfish, Cyprinodon rubrofluviatilis

3. Organisms and the abiotic environment
red creek
Cyprinodon rubrofluviatilis

4. Organisms and the abiotic environment

5. Organisms and the abiotic environment
broad tolerance for environmental conditions:
temperature (eurythermal)
salinity (euryhaline)
oxygen concentration (euryoxic)

6. Organisms and the abiotic environment

7. Organisms and the abiotic environment
The Southern Redbelly Dace, Phoxinus erythrogaster

8. Organisms and the abiotic environment
Phoxinus erythrogaster
the Blue River

9. Organisms and the abiotic environment

10. Organisms and the abiotic environment
narrow tolerance for environmental conditions:
temperature (stenothermal)
salinity (stenohaline)
oxygen concentration (stenoxic)

11. Distribution and abundance of organisms
A species’ tolerance for abiotic environmental conditions is one factor that affects its distribution and abundance

12. Distribution and abundance of organisms
Some species are widespread and common

13. Distribution and abundance of organisms
Other species are localized and rare
‘akiapola’au
the Rich Mountain salamander

14. Distribution and abundance of organisms
The distribution and abundance of species changes over time
Some species decline in abundance and extent of geographic range

15. Distribution and abundance of organisms
The distribution and abundance of species changes over time
Other species increase in abundance and expand in range

16. Distribution and abundance of organisms
The causes of these changes include…
geological change
climate change
change in the biotic environment
“anthropogenic” factors

17. Population ecology
Ecologists are concerned with how population size changes…
All populations have the capacity to increase in size
This capacity is the “biotic potential” of the population
and with the factors that regulate change
through reproduction by the individuals in the population

18. Population ecology
Biotic potential is the rate at which a population would grow with no limitation on resources and no mortality due to predation or other factors
Under these conditions populations grow exponentially…

19. Population ecology Exponential population growth:
Change in population size over time is a function of the current population size and the biotic potential of the population

20. Population ecology dN/dt = r N
as time passes, more individuals are added to the population
number of individuals added is a function of the population size

21. Population ecology dN/dt = r N
with no constraints, a population grows exponentially

22. Population ecology But there are constraints…
food, space, nest sites, etc become limiting
intraspecific competition for resources slows population growth

23. Population ecology
the populaiton size that the resources of a habitat can support is the “carrying capacity”

24. Population ecology
dN/dt = r N(K-N/K)
Where K is the carrying capacity

25. Population ecology dN/dt = r N(K-N/K)
What happens to dN/dt when N is small relative to K?

26. Population ecology dN/dt = r N(K-N/K)
What happens to dN/dt as N approaches K?

27. Population ecology
“Logistic” population growth

28. Population ecology What factors regulate population growth?
Density-dependent factors:
intraspecific competition

29. Population ecology What factors regulate population growth?
Density-dependent factors:
intraspecific competition
predation

30. Population ecology What factors regulate population growth?
Density-dependent factors:
intraspecific competition
predation
disease and parasitism

31. Population ecology What factors regulate population growth?
Density-independent factors:
weather; drought, flood, storm, heat, cold

32. Population ecology What factors regulate population growth?
Density-independent factors:
weather; drought, flood, storm, heat, cold
catastrophes

33. Life history strategy
Population growth depends on reproduction by individuals in the population
Natural selection acts on characteristics that affect the balance between “somatic growth” and “reproductive growth” over the lifespan of individuals.
The balance between “somatic growth” and “reproductive growth” over the lifespan of individuals is “life history strategy”

34. Life history strategy
There are two extremes in the spectrum of life history strategy…

35. Life history strategy
There are two extremes in the spectrum of life history strategy…
“r” selected species emphasize biotic potential, the ability to increase in population size quickly

36. Life history strategy
There are two extremes in the spectrum of life history strategy…
“r” selected species emphasize biotic potential, the ability to increase in population size quickly
“K” selected species emphasize stable population size, at or near K

37. Life history strategy “r” selected species…
high intrinsic rate of increase
small body size (usually)
rapid ontogenetic development
early reproductive maturity
large numbers of small offspring
short life span
poor competitors for space, light…
highly variable population size
often density independent regulation of population size
often inhabit variable, unpredictable, or disturbed habitats
good dispersal and colonizing capabilities

38. Life history strategy
“K” selected species emphasize stable population size, at or near K

39. Life history strategy “K” selected species…
low intrinsic rate of increase
large body size (usually)
slow ontogenetic development
late reproductive maturity
small numbers of large offspring
long life span
good competitors…
stable population size, near K
often density dependent regulation of population size
often inhabit stable, predictable, or undisturbed habitats
population size at equilibrium